Question: Http://www.sciencedirect.com/science/article/pii/S0960982214004643 1. The authors refer to Disrup…

http://www.sciencedirect.com/science/article/pii/S0960982214004643

1. The authors refer to Disruptive Selection, but their study
specifically involves a single gene, with two alleles in which the
heterozygote has the lowest fitness. What would be the expected
outcome in a finite population in the single gene case vs. the
expected phenotypic distribution if the phenotype were
polygenic?

2. The authors briefly discuss the fitness effects of the two
most frequent plate morphs Low (LL) and Complete (CC). What are
some potential fitness effects of these genotypes in this lake
and/or in any other stickleback habitat?

3. The authors mention that a polymorphism in a case like this
could be maintained if there were gene flow from other populations.
Explain how this would work. Keep in mind the expected result that
you described for the single gene case in question 1. Why do the
authors believe that gene flow from outside the lake is not a
factor in this case?

4. The authors refer to Assortative Mating on several occasions.
In this case, that would be preferential mating between individuals
with similar phenotypes. Why might such a mate preference be
expected to evolve in either a polygenic case of disruptive
selection or a single gene case like this one? Is there evidence
that assortative mating is or is not occurring and what is it?

5. The authors suggest that negative frequency dependent
selection could play a role in maintaining this polymorphism.
Explain how that would counteract the expected long term result of
heterozygotes having the lowest fitness. The authors have a few
suggestions as to the specifics of such frequency-dependent
selection. You can use one or more of these as an example.